U.S. patent number 11,357,467 [Application Number 16/694,192] was granted by the patent office on 2022-06-14 for multi-pass computed tomography scans for improved workflow and performance.
This patent grant is currently assigned to Accuray, Inc.. The grantee listed for this patent is Accuray, Inc.. Invention is credited to Chuanyong Bai, Daniel Gagnon, Zhicong Yu.
United States Patent |
11,357,467 |
Gagnon , et al. |
June 14, 2022 |
Multi-pass computed tomography scans for improved workflow and
performance
Abstract
An x-ray imaging apparatus and associated methods are provided
to execute multi-pass imaging scans for improved quality and
workflow. An imaging scan can be segmented into multiple passes
that are faster than the full imaging scan. Data received by an
initial scan pass can be utilized early in the workflow and of
sufficient quality for treatment setup, including while the another
scan pass is executed to generate data needed for higher quality
images, which may be needed for treatment planning. In one
embodiment, a data acquisition and reconstruction technique is used
when the detector is offset in the channel and/or axial direction
for a large FOV during multiple passes.
Inventors: |
Gagnon; Daniel (Twinsburg,
OH), Bai; Chuanyong (Solon, OH), Yu; Zhicong
(Highland Hts., OH) |
Applicant: |
Name |
City |
State |
Country |
Type |
Accuray, Inc. |
Sunnyvale |
CA |
US |
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Assignee: |
Accuray, Inc. (Sunnyvale,
CA)
|
Family
ID: |
1000006367011 |
Appl.
No.: |
16/694,192 |
Filed: |
November 25, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200170591 A1 |
Jun 4, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62878364 |
Jul 25, 2019 |
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62743796 |
May 6, 2019 |
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62836357 |
Apr 19, 2019 |
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62836352 |
Apr 19, 2019 |
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62821116 |
Mar 20, 2019 |
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62813335 |
Mar 4, 2019 |
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62801260 |
Feb 5, 2019 |
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62800287 |
Feb 1, 2019 |
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62796831 |
Jan 25, 2019 |
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62773700 |
Nov 30, 2018 |
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62773712 |
Nov 30, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
6/032 (20130101); A61B 6/4078 (20130101); G06T
11/005 (20130101); A61B 6/06 (20130101); A61B
6/5205 (20130101); A61B 6/488 (20130101); A61B
6/027 (20130101); A61B 6/5282 (20130101); A61B
6/4085 (20130101); A61B 6/469 (20130101); A61B
6/405 (20130101); A61N 5/1071 (20130101); A61N
5/107 (20130101); A61B 6/541 (20130101); G06T
2207/10081 (20130101); A61N 2005/1095 (20130101); A61B
6/482 (20130101); G06T 2211/412 (20130101); A61N
5/1082 (20130101); A61B 6/08 (20130101); A61B
6/4458 (20130101); A61B 6/484 (20130101); A61B
6/582 (20130101); A61N 5/1049 (20130101); A61B
5/055 (20130101); A61B 6/4441 (20130101); A61B
6/4435 (20130101); A61B 6/481 (20130101); A61B
6/0407 (20130101); A61B 6/483 (20130101); G06T
2211/424 (20130101); A61B 6/025 (20130101); A61B
6/4014 (20130101); G06T 2211/404 (20130101); G06T
7/30 (20170101); A61N 5/1067 (20130101); G06T
11/008 (20130101); G06T 2210/41 (20130101); A61B
6/03 (20130101); G06T 2211/432 (20130101); A61N
2005/1085 (20130101); A61B 6/035 (20130101); A61B
6/4064 (20130101); A61B 6/4028 (20130101); G06T
2211/428 (20130101); A61N 2005/1091 (20130101); A61B
6/4021 (20130101) |
Current International
Class: |
A61B
6/00 (20060101); G06T 11/00 (20060101); A61B
6/02 (20060101); A61B 6/06 (20060101); A61B
6/03 (20060101); A61B 6/04 (20060101); A61N
5/10 (20060101); A61B 6/08 (20060101); G06T
7/30 (20170101); A61B 5/055 (20060101) |
References Cited
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WO |
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WO |
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2018/183748 |
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Oct 2018 |
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WO |
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Primary Examiner: Song; Hoon K
Attorney, Agent or Firm: Calfee, Halter & Griswold
LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of eleven U.S. provisional
patent applications, including Ser. No. 62/773,712, filed Nov. 30,
2018; Ser. No. 62/773,700, filed Nov. 30, 2018; Ser. No.
62/796,831, filed Jan. 25, 2019; Ser. No. 62/800,287, filed Feb. 1,
2019; Ser. No. 62/801,260, filed Feb. 5, 2019; Ser. No. 62/813,335,
filed Mar. 4, 2019; Ser. No. 62/821,116, filed Mar. 20, 2019; Ser.
No. 62/836,357, filed Apr. 19, 2019; Ser. No. 62/836,352, filed
Apr. 19, 2019; Ser. No. 62/843,796, filed May 6, 2019; and Ser. No.
62/878,364, filed Jul. 25, 2019. This application is also related
to ten non-provisional U.S. patent applications filed on the same
day, including Ser. No. 16/694,145, filed Nov. 25, 2019, entitled
"MULTIMODAL RADIATION APPARATUS AND METHODS;" Ser. No. 16/694,148,
filed Nov. 25, 2019, entitled "APPARATUS AND METHODS FOR SCALABLE
FIELD OF VIEW IMAGING USING A MULTI-SOURCE SYSTEM;" Ser. No.
16/694,161, filed Nov. 25, 2019, entitled "INTEGRATED HELICAL
FAN-BEAM COMPUTED TOMOGRAPHY IN IMAGE-GUIDED RADIATION TREATMENT
DEVICE;" Ser. No. 16/694,166, filed Nov. 25, 2019, entitled
"COMPUTED TOMOGRAPHY SYSTEM AND METHOD FOR IMAGE IMPROVEMENT USING
PRIOR IMAGE;" Ser. No. 16/694,177, filed Nov. 25, 2019, entitled
"OPTIMIZED SCANNING METHODS AND TOMOGRAPHY SYSTEM USING REGION OF
INTEREST DATA;" Ser. No. 16/694,190, filed Nov. 25, 2019, entitled
"HELICAL CONE-BEAM COMPUTED TOMOGRAPHY IMAGING WITH AN OFF-CENTERED
DETECTOR;" Ser. No. 16/694,202, filed Nov. 25, 2019, entitled
"METHOD AND APPARATUS FOR SCATTER ESTIMATION IN CONE-BEAM COMPUTED
TOMOGRAPHY;" Ser. No. 16/694,210, filed Nov. 25, 2019, entitled
"ASYMMETRIC SCATTER FITTING FOR OPTIMAL PANEL READOUT IN CONE-BEAM
COMPUTED TOMOGRAPHY;" Ser. No. 16/694,218, filed Nov. 25, 2019,
entitled "METHOD AND APPARATUS FOR IMPROVING SCATTER ESTIMATION AND
CORRECTION IN IMAGING;" and Ser. No. 16/694,230, filed Nov. 25,
2019, entitled "METHOD AND APPARATUS FOR IMAGE RECONSTRUCTION AND
CORRECTION USING INTER-FRACTIONAL INFORMATION." The contents of all
above-identified patent application(s) and patent(s) are fully
incorporated herein by reference.
Claims
The invention claimed is:
1. An x-ray imaging apparatus for multi-pass scans, comprising: a
rotatable gantry system positioned at least partially around a
patient support; a first radiation source coupled to the rotatable
gantry system, the first radiation source configured as an imaging
radiation source; a radiation detector coupled to the rotatable
gantry system and positioned to receive radiation from the first
radiation source during an imaging scan; a controller configured
to: move the patient support relative to the rotatable gantry
system during a first pass of the imaging scan; move the patient
support relative to the rotatable gantry system during a second
pass of the imaging scan; a data processing system configured to:
receive first imaging data measured by the radiation detector
during the first pass; receive second imaging data measured by the
radiation detector during the second pass; combine the first
imaging data and the second imaging data into a combined imaging
dataset; and reconstruct a second patient image using the combined
imaging dataset; wherein a relative axial position of the first
radiation source and the radiation detector is shifted during the
second pass relative to the first pass, and wherein the first
imaging data and the second imaging data are used jointly during
reconstruction of the second patient image.
2. The apparatus of claim 1, wherein the data processing system is
further configured to reconstruct a first patient image based on
the first imaging data, wherein the first patient image is
reconstructed during the second pass.
3. The apparatus of claim 1, wherein a scanning parameter for the
second pass is determined based on the first imaging data.
4. The apparatus of claim 3, wherein the data processing system is
further configured to reconstruct a first patient image based on
the first imaging data, and wherein the first patient image is
registered with a planning image to determine the scanning
parameter.
5. The apparatus of claim 3, wherein the scanning parameter
comprises at least one of a pitch, an energy level, a tube
potential, a tube current, a pulse width, a beam filter, or a
speed.
6. The apparatus of claim 1, wherein the first pass comprises a
first tube energy of the first radiation source and the second pass
comprises a second tube energy of the first radiation source, and
wherein the second patient image comprises a spectral patient
image.
7. The apparatus of claim 1, wherein the data processing system is
further configured to reconstruct a first patient image based on
the first imaging data, and wherein a treatment setup is based on
the first patient image and a treatment plan is based on the second
patient image.
8. The apparatus of claim 7, wherein the treatment setup comprises
registering the first patient image with a planning image.
9. The apparatus of claim 1, wherein the patient support moves in a
first longitudinal direction during the first pass and moves in a
second longitudinal direction during the second pass, and wherein
the second direction is opposite the first direction.
10. The apparatus of claim 1, wherein the patient support moves at
a first speed during the first pass and moves in at a second speed
during the second pass, and wherein the first speed is faster than
the second speed.
11. The apparatus of claim 1, wherein the first pass and the second
pass comprise helical scans.
12. The apparatus of claim 1, wherein the first pass is completed
in a first time and the second pass is completed in a second time,
and wherein the second time is longer than the first time.
13. The apparatus of claim 1, wherein the second pass comprises
more views than the first pass.
14. The apparatus of claim 1, wherein the radiation detector is
offset in one transaxial direction during the first pass and offset
in an opposite transaxial direction during the second pass.
15. The apparatus of claim 1, further comprising a second radiation
source coupled to the rotatable gantry system, the second radiation
source configured as a therapeutic radiation source, wherein the
second radiation source delivers a dose of radiation calculated
based on the second patient image.
16. A method of collecting imaging data during a multi-pass scan,
comprising: moving a patient support relative to a rotatable gantry
system during a first pass of an imaging scan, wherein a first
radiation source and a radiation detector are coupled to the
rotatable gantry system positioned at least partially around the
patient support; receiving first imaging data measured by the
radiation detector during the first pass; moving the patient
support relative to the rotatable gantry system during a second
pass of the imaging scan; receiving second imaging data measured by
the radiation detector during the second pass; combining the first
imaging data and the second imaging data to form a combined imaging
dataset; reconstructing a patient image using the combined imaging
dataset; registering the first image with a planning image for
treatment setup; and calculating a therapeutic radiation dose based
on the second patient image.
17. The method of claim 16, wherein the patient support moves in a
first longitudinal direction during the first pass and moves in a
second longitudinal direction during the second pass, and wherein
the second direction is opposite the first direction.
18. A radiotherapy delivery device comprising: a rotatable gantry
system positioned at least partially around a patient support; a
first radiation source coupled to the rotatable gantry system, the
first radiation source configured as an imaging radiation source; a
second radiation source coupled to the rotatable gantry system, the
second radiation source configured as a therapeutic radiation
source a radiation detector coupled to the rotatable gantry system
and positioned to receive radiation from the first radiation source
during an imaging scan; a controller configured to: move the
patient support relative to the rotatable gantry system during a
first pass of the imaging scan; move the patient support relative
to the rotatable gantry system during a second pass of the imaging
scan; a data processing system configured to: receive first
projection data measured by the radiation detector during the first
pass; reconstruct a first patient image based on the first
projection data; receive second projection data measured by the
radiation detector during the second pass; and reconstruct a second
patient image based on the first projection data and the second
projection data; wherein a treatment setup is based on the first
patient image, and wherein the second radiation source delivers a
dose of radiation calculated based on the second patient image
during adaptive IGRT.
Description
FIELD OF THE INVENTION
Aspects of the disclosed technology relate to computed tomography
imaging, and, more particularly, to an apparatus and method for
multi-pass scans associated with imaging, data reconstruction, and
workflows, including when utilizing an off-centered (offset)
detector during cone-beam computed tomography helical scans.
BACKGROUND
Computed tomography (CT) imaging, including cone-beam computed
tomography (CBCT), is a valuable tool in radiotherapy. It can be
used for patient positioning and dose calculation. It also has the
potential to allow physicians to perform adaptive radiotherapy,
including in the context of image-guided radiation treatment
(IGRT). IGRT can make use of medical imaging technology, such as
CT, to collect images of a patient before, during, and/or after
treatment.
One popular data acquisition form is a circular scan, with a
centered detector for small-object scans (e.g., head), and an
off-centered (offset or shifted) detector in the channel direction
for large object-scans (e.g., abdomen). For most radiotherapy
systems, a circular scan is likely the only practical choice, as
the gantry can only rotate in one direction for a limited number of
degrees, thus preventing these machines from using a helical source
trajectory. A helical scan can provide higher quality images with
less artifacts, reduced scatter, and faster scanning when compared
to circular scans, but view completion is much more complex.
CT images acquired on an IGRT system have two major applications:
(a) registration with a planning CT image for patient treatment
setup; and (b) adaptive planning and dose calculation. The
requirements of the CT images for the two applications can be
different. For registration and treatment setup, absolute accuracy
in CT quantitation (such as CT numbers) is not as critical as for
adaptive planning and dose calculation, yet relatively large axial
field-of-view (FOV) is allowed for registration and setup
accuracy.
BRIEF SUMMARY
In one embodiment, a method of collecting imaging data during a
multi-pass scan includes moving a patient support relative to a
rotatable gantry system during a first pass of an imaging scan,
wherein a first radiation source and a radiation detector are
coupled to the rotatable gantry system positioned at least
partially around the patient support, receiving first projection
data measured by the radiation detector during the first pass,
moving the patient support relative to the rotatable gantry system
during a second pass of the imaging scan, receiving second
projection data measured by the radiation detector during the
second pass, and reconstructing a patient image based on the first
projection data and the second projection data.
Features that are described and/or illustrated with respect to one
embodiment may be used in the same way or in a similar way in one
or more other embodiments and/or in combination with or instead of
the features of the other embodiments.
The descriptions of the invention do not limit the words used in
the claims in any way or the scope of the claims or invention. The
words used in the claims have all of their full ordinary
meanings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which are incorporated in and
constitute a part of the specification, embodiments of the
invention are illustrated, which, together with a general
description of the invention given above, and the detailed
description given below, serve to exemplify embodiments of this
invention. It will be appreciated that illustrated element
boundaries (e.g., boxes, groups of boxes, or other shapes) in the
figures represent one embodiment of boundaries. In some
embodiments, one element may be designed as multiple elements or
that multiple elements may be designed as one element. In some
embodiments, an element shown as an internal component of another
element may be implemented as an external component and vice versa.
Furthermore, elements may not be drawn to scale.
FIG. 1 is a perspective view of an exemplary x-ray imaging
apparatus in accordance with one aspect of the disclosed
technology.
FIG. 2 is a diagrammatic illustration of an x-ray imaging apparatus
integrated into an exemplary radiotherapy device in accordance with
one aspect of the disclosed technology.
FIG. 3 is an illustration of an exemplary x-ray imaging apparatus
shown with a world coordinate system defined.
FIG. 4 is an illustration of an exemplary x-ray imaging apparatus
shown with a patient support moving into a gantry during one scan
pass.
FIG. 5 is an illustration of an exemplary x-ray imaging apparatus
shown with a patient support moving out of the gantry during
another scan pass.
FIG. 6 is an illustration of exemplary trajectories associated with
two interleaved scans during a dual-pass helical scan protocol with
a large pitch for fast scanning.
FIG. 7 is an illustration of the 3D geometry of an exemplary data
acquisition system.
FIG. 8 is an illustration of the geometry of a data acquisition
system in an exemplary (x, z)-plane.
FIG. 9A is an illustration of an exemplary scan trajectory and
offset detector position during a left-handed helix.
FIG. 9B is an illustration of an exemplary scan trajectory and
offset detector position during a right-handed helix.
FIG. 10 is an illustration of the data availability during the
scans shown in FIGS. 9A and 9B in an exemplary transverse
plane.
FIG. 11 shows exemplary reconstructions of a thorax phantom using
the scans shown in FIGS. 9A and 9B.
FIG. 12 is a flow chart of an exemplary multi-pass imaging
process.
FIG. 13 is a flow chart of another exemplary multi-pass imaging
process.
FIG. 14 is a flow chart of another exemplary multi-pass imaging
process.
FIG. 15 is a flow chart of another exemplary multi-pass imaging
process.
FIG. 16 is a flow chart depicting an exemplary method of IGRT using
a radiotherapy device.
FIG. 17 is a block diagram depicting exemplary image-based
pre-delivery steps.
FIG. 18 is a block diagram depicting exemplary data sources that
may be utilized during imaging or image-based pre-delivery
steps.
DETAILED DESCRIPTION
The following includes definitions of exemplary terms that may be
used throughout the disclosure. Both singular and plural forms of
all terms fall within each meaning.
"Component," as used herein can be defined as a portion of
hardware, a portion of software, or a combination thereof. A
portion of hardware can include at least a processor and a portion
of memory, wherein the memory includes an instruction to execute. A
component may be associated with a device.
"Logic," synonymous with "circuit" as used herein, includes but is
not limited to hardware, firmware, software and/or combinations of
each to perform a function(s) or an action(s). For example, based
on a desired application or needs, logic may include a
software-controlled microprocessor, discrete logic such as an
application specific integrated circuit (ASIC), or other programmed
logic device and/or controller. Logic may also be fully embodied as
software.
"Processor," as used herein includes, but is not limited to, one or
more of virtually any number of processor systems or stand-alone
processors, such as microprocessors, microcontrollers, central
processing units (CPUs), and digital signal processors (DSPs), in
any combination. The processor may be associated with various other
circuits that support operation of the processor, such as
random-access memory (RAM), read-only memory (ROM), programmable
read-only memory (PROM), erasable programmable read-only memory
(EPROM), clocks, decoders, memory controllers, or interrupt
controllers, etc. These support circuits may be internal or
external to the processor or its associated electronic packaging.
The support circuits are in operative communication with the
processor. The support circuits are not necessarily shown separate
from the processor in block diagrams or other drawings.
"Signal," as used herein includes, but is not limited to, one or
more electrical signals, including analog or digital signals, one
or more computer instructions, a bit or bit stream, or the
like.
"Software", as used herein, includes but is not limited to one or
more computer readable and/or executable instructions that cause a
computer, processor, logic, and/or other electronic device to
perform functions, actions, and/or behave in a desired manner. The
instructions may be embodied in various forms such as routines,
algorithms, modules, or programs including separate applications or
code from dynamically linked sources or libraries.
While the above exemplary definitions have been provided, it is
Applicant's intention that the broadest reasonable interpretation
consistent with this specification be used for these and other
terms.
As is discussed in more detail below, embodiments of the disclosed
technology relate to multi-pass scans for improved workflow and/or
performance. In some embodiments, a radiotherapy delivery device
and method can make use of an integrated low-energy radiation
source for CT for use in conjunction with or as part of IGRT. In
particular, for example, a radiotherapy delivery device and method
can combine a low-energy collimated radiation source for imaging in
a gantry using rotational image acquisition along with a
high-energy radiation source for therapeutic treatment. In various
embodiments, the low-energy radiation source (e.g., kV) can produce
higher quality images than via use of the high-energy radiation
source (e.g., MV) for imaging. Images generated with kV energy can
have better tissue contrast than with MV energy. High quality
volume imaging can be needed for visualization of targets and
organs-at-risk (OARS), for adaptive therapy monitoring, and for
treatment planning/re-planning. In some embodiments, the kV imaging
system can also be used for positioning, motion tracking, and/or
characterization or correction capabilities.
The image acquisition methodology can include or otherwise make use
of a multiple rotation scan, which may be, for example, a
continuous scan (e.g., with a helical source trajectory about a
central axis together with longitudinal movement of a patient
support through a gantry bore), a non-continuous circular
stop-and-reverse scan with incremental longitudinal movement of a
patient support, etc.
In accordance with various embodiments, the x-ray imaging apparatus
collimates a radiation source, including, for example, into a cone
beam or a fan beam using, for example, a beamformer. In one
embodiment, the collimated beam can be combined with a gantry that
continuously rotates while the patient moves, resulting in a
helical image acquisition.
In some embodiments, the time associated with increased scanning
rotations to complete a high-quality volume image may be mitigated
by high gantry rates/speed (e.g., using fast slip ring rotation,
including, e.g., up to 10 revolutions per minute (rpm), up to 20
rpm, up to 60 rpm, or more rpm), high kV frame rates, and/or sparse
data reconstruction techniques, to provide kV CT imaging on a
radiation therapy delivery platform. Detectors (with various
row/slice sizes, configurations, dynamic range, etc.), scan pitch,
and/or dynamic collimation are additional features in various
embodiments, including to selectively expose portions of the
detector and selectively define active readout areas.
A helical scan trajectory can have several advantages in view of a
circular scan. For example, cone-beam artifacts are reduced because
a helical scan can provide more complete projection data for image
reconstruction. Also, a helical scan can acquire projection data
for a large longitudinal coverage with a narrow axial opening,
which could substantially reduce scatter contamination in the
projection data. Reconstructed images can have significantly
improved image quality in terms of low frequency artifacts and
result in greatly enhanced soft-tissue contrast. Furthermore, a
helical scan can improve scan speed with a large pitch.
With reference to FIG. 1 and FIG. 2, an x-ray imaging apparatus 10
is shown. It will be appreciated that the x-ray imaging apparatus
10 may be associated with and/or integrated into a radiotherapy
device (as shown in FIG. 2) that can be used for a variety of
applications, including, but not limited to IGRT. The x-ray imaging
apparatus 10 includes a rotatable gantry system, referred to as
gantry 12 supported by or otherwise housed in a support unit or
housing 14. Gantry herein refers to a gantry system that comprises
one or more gantries (e.g., ring or C-arm) capable of supporting
one or more radiation sources and/or associated detectors as they
rotate around a target. For example, in one embodiment, a first
radiation source and its associated detector may be mounted to a
first gantry of the gantry system and a second radiation source and
its associated detector may be mounted to a second gantry of the
gantry system. In another embodiment, more than one radiation
source and associated detector(s) may be mounted to the same gantry
of the gantry system, including, for example, where the gantry
system is comprised of only one gantry. Various combinations of
gantries, radiation sources, and radiation detectors may be
combined into a variety of gantry system configurations to image
and/or treat the same volume within the same apparatus. For
example, kV and MV radiation sources can be mounted on the same or
different gantries of the gantry system and selectively used for
imaging and/or treatment as part of an IGRT system. If mounted to
different gantries, the radiation sources are able to rotate
independently, but are still able to simultaneously image the same
(or nearly the same) volume. A rotatable ring gantry 12 may be
capable of 10 rpm or more, as mentioned above. The rotatable gantry
12 defines a gantry bore 16 into and through which a patient can be
moved and positioned for imaging and/or treatment. In accordance
with one embodiment, the rotatable gantry 12 is configured as a
slip ring gantry to provide continuous rotation of an imaging
radiation source (e.g., x-ray) and an associated radiation detector
while providing sufficient bandwidth for the high-quality imaging
data received by the detector. A slip-ring gantry can eliminate
gantry rotations in alternating directions in order to wind and
unwind cables carrying the power and signals associated with the
device. Such a configuration will allow for continuous helical
(e.g., fan-beam, cone-beam, etc.) computed tomography, even when
integrated into an IGRT system.
A patient support 18 or table/couch is positioned adjacent to the
rotatable gantry 12 and configured to support a patient, typically
in a horizontal position, for longitudinal movement into and within
the rotatable gantry 12. The patient support 18 can move the
patient, for example, in a direction perpendicular to the plane of
rotation of the gantry 12 (along or parallel to the rotation axis
of the gantry 12). The patient support 18 can be operatively
coupled to a patient support controller for controlling movement of
the patient and patient support 18. The patient support controller
can be synchronized with the rotatable gantry 12 and sources of
radiation mounted to the rotating gantry for rotation about a
patient longitudinal axis in accordance with a commanded imaging
and/or treatment plan. In some embodiments, the patient support can
also be moved in a limited range up and down, left and right once
it is in the bore 16 to adjust the patient position for optimal
treatment.
As shown in FIG. 2, the x-ray imaging apparatus 10 includes a
source of imaging radiation 30 coupled to or otherwise supported by
the rotatable gantry 12. The source of imaging radiation 30 emits a
radiation beam (indicated generally as 32) for generating
high-quality images. In this embodiment, the source of imaging
radiation is an x-ray source 30, configured as a kilovoltage (kV)
source (e.g., a clinical x-ray source having an energy level in the
range of about 20 kV to about 150 kV). In one embodiment, the kV
source of radiation comprises a kilo-electron volt peak photon
energy (keV) up to 150 keV. The imaging radiation source can be any
type of transmission source suitable for imaging. For example, the
imaging radiation source may be, for example, an x-ray generating
source (including for CT) or any other way to produce photons with
sufficient energy and flux (such as, e.g., a gamma-source (e.g.,
Cobalt-57, energy peak at 122 keV), an x-ray fluorescence source
(such as fluorescence source through Pb k lines, two peaks @about
70 keV and @about 82 keV), etc.). References herein to x-ray, x-ray
imaging, x-ray imaging source, etc. are exemplary for particular
embodiments. Other imaging transmission sources can be used
interchangeably in various other embodiments. An x-ray detector 34
(e.g., two-dimensional flat detector or curved detector) can be
coupled to or otherwise supported by the rotatable gantry 12. The
x-ray detector 34 is positioned to receive radiation from the x-ray
source 30 and can rotate along with the x-ray source 30. The
detector 34 can detect or otherwise measure the amount of radiation
not attenuated and therefore infer what was in fact attenuated by
the patient or associated patient ROI (by comparison to what was
initially generated). The detector 34 can detect or otherwise
collect attenuation data from different angles as the x-ray source
30 rotates around and emits radiation toward the patient.
It will be appreciated that the x-ray detector 34 can take on a
number of configurations without departing from the scope of the
disclosed technology. As illustrated in FIG. 2, the x-ray detector
34 can be configured as a flat-panel detector (e.g., a multi-row
flat panel detector). In accordance with another exemplary
embodiment, the x-ray detector 34 can be configured as a curved
detector. The detector 34 can be adjusted to an offset (i.e.,
shifted) position in the channel and/or axial direction.
Although FIGS. 1 and 2 depict an x-ray imaging apparatus 10 with a
radiation source 30 mounted to a ring gantry 12, other embodiments
may include other types of rotatable imaging apparatuses,
including, for example, C-arm gantries and robotic arm-based
systems. In gantry-based systems, a gantry rotates the imaging
radiation source 30 around an axis passing through the isocenter.
Gantry-based systems include C-arm gantries, in which the imaging
radiation source 30 is mounted, in a cantilever-like manner, over
and rotates about the axis passing through the isocenter.
Gantry-based systems further include ring gantries, for example,
rotatable gantry 12, having generally toroidal shapes in which the
patient's body extends through a bore of the ring/toroid, and the
imaging radiation source 30 is mounted on the perimeter of the ring
and rotates about the axis passing through the isocenter. In some
embodiments, the gantry 12 rotates continuously. In other
embodiments, the gantry 12 utilizes a cable-based system that
rotates and reverses repeatedly.
A collimator or beamformer assembly (indicated generally as 36) is
positioned relative to the x-ray source 30 to selectively control
and adjust a shape of a radiation beam 32 emitted by the x-ray
source 30 to selectively expose a portion or region of the active
area of the x-ray detector 34. The beamformer can also control how
the radiation beam 32 is positioned on the x-ray detector 34. In
one embodiment, the beamformer 36 could have one degree/dimension
of motion (e.g., to make a thinner or fatter slit). In another
embodiment, the beamformer 36 can have two degrees/dimensions of
motion (e.g., to make various sized rectangles). In other
embodiments, the beamformer 36 may be capable of various other
dynamically-controlled shapes, including, for example,
parallelograms. All of these shapes may be dynamically adjusted
during a scan. In some embodiments, blocking portions of the
beamformer can be rotated and translated.
The beamformer 36 can be controlled to adjust the shape of the
radiation beam 32 emitted by the x-ray source 30 dynamically in a
number of geometries, including, but not limited to, a fan beam or
cone beam having a beam thickness (width) as low as one detector
row width or including multiple detector rows, which will be only a
portion of the detector's active area. In various embodiments, the
thickness of the beam may expose several centimeters of a larger
detector active area. For example, 3-4 centimeters (measured in the
longitudinal direction in the detector plane) of a 5-6 centimeter
detector may be selectively exposed to the imaging radiation 32. In
this embodiment, 3-4 centimeters of projection image data may be
captured with each readout, with about 1-2 centimeters of unexposed
detector area on one or each side, which may be used to capture
scatter data, as discussed below.
In other embodiments, more or less of a portion of the active
detector may be selectively exposed to the imaging radiation. For
example, in some embodiments, the beam thickness may be reduced
down to about two centimeters, one centimeter, less than one
centimeter, or ranges of similar sizes, including with smaller
detectors. In other embodiments, the beam thickness may be
increased to about 4 centimeters, 5 centimeters, greater than 5
centimeters, or ranges of similar sizes, including with larger
detectors. In various embodiments, the ratio of exposed-to-active
detector area may be 30-90% or 50-75%. In other embodiments, the
ratio of exposed-to-active detector area may be 60-70%. However,
various other exposed and active area sizes or ratios of
exposed-to-active detector area may be suitable in other
embodiments. The beam and detector can be configured so that the
shadowed region of the detector (active but not exposed to direct
radiation) is sufficient to capture scatter data beyond the
penumbra region.
Various embodiments may include an optimization of the features
that control selective exposure of the detector 34 (e.g., beam
size, beam/aperture center, collimation, pitch, detector readout
range, detector readout center, etc.) such that the measured data
is sufficient for primary (exposed) and shadowed regions, but also
optimized for speed and dosage control. The beamformer 36
shape/position and detector 34 readout range can be controlled such
that the radiation beam 32 from the x-ray source 30 covers as much
or as little of the x-ray detector 34 based on the particular
imaging task being carried out. The beam 32 can be shaped to be
various shapes, including, for example, parallelograms. The
beamformer 36 can be configured to adjust the shape of the
radiation beam 32 by rotation and/or translation of x-ray
attenuated material of the beamformer 36.
The collimator/beamformer 36 may be configured in a variety of ways
that allow it to adjust the shape of the radiation beam 32 emitted
by the x-ray source 30. For example, the collimator 36 can be
configured to include a set of jaws or other suitable members that
define and selectively adjust the size of an aperture through which
the radiation beam from the x-ray source 30 may pass. In accordance
with one exemplary configuration, the collimator 36 can include an
upper jaw and a lower jaw, where the upper and lower jaws are
movable in different directions (e.g., parallel directions) to
adjust the size of the aperture through which the radiation beam
from the x-ray source 30 passes, and also to adjust the beam
position relative to the patient to illuminate only the portion of
the patient to be imaged for optimized imaging and minimized
patient dose.
In accordance with one embodiment, the shape of the radiation beam
32 from the x-ray source 30 can be changed during an image
acquisition. Stated differently, in accordance with one exemplary
implementation, the beamformer 36 leaf positions and/or aperture
width can be adjusted before or during a scan. For example, in
accordance with one embodiment, the beamformer 36 can be
selectively controlled and dynamically adjusted during rotation of
the x-ray source 30 such that the radiation beam 32 has a shape
with sufficient primary/shadow regions and is adjusted to include
only an object of interest during imaging (e.g., the prostate). The
shape of the radiation beam 32 being emitted by the x-ray source 30
can be changed during or after a scan, depending on the desired
image acquisition, which may be based on imaging and/or therapeutic
feedback, as discussed in more detail below.
As shown in FIG. 2, the x-ray imaging apparatus 10 may be
integrated with a radiotherapy device that includes a therapeutic
radiation source 20 coupled to or otherwise supported by the
rotatable gantry 12. In accordance with one embodiment, the
therapeutic radiation source 20 is configured as a source of
therapeutic radiation, such as a high-energy source of radiation
used for treatment of a tumor within a patient in a region of
interest. It will be appreciated that the source of therapeutic
radiation can be a high-energy x-ray beam (e.g., megavoltage (MV)
x-ray beam), and/or a high-energy particle beam (e.g., a beam of
electrons, a beam of protons, or a beam of heavier ions, such as
carbon) or another suitable form of high-energy radiation. In one
embodiment, the first source of radiation 20 comprises a
mega-electron volt peak photon energy (MeV) of 1 MeV or greater. In
one embodiment, the high-energy x-ray beam has an average energy
greater than 0.8 MeV. In another embodiment, the high-energy x-ray
beam has an average energy greater than 0.2 MeV. In another
embodiment, the high-energy x-ray beam has an average energy
greater than 150 keV. Generally, the first source of radiation 20
has a higher energy level (peak and/or average, etc.) than the
second source of radiation 30.
In one embodiment, the therapeutic radiation source 20 is a linear
accelerator (LINAC) producing therapeutic radiation (e.g., MV
source) and the imaging system comprises an independent x-ray
imaging source of radiation producing relatively low intensity and
lower energy imaging radiation (e.g., kV source). In other
embodiments, the therapeutic radiation source 20 could be a
radioisotope, such as, for example, Co-60, and it can generally
have energy >1 MeV. The therapeutic radiation source 20 can emit
one or more beams of radiation (indicated generally by 22) toward a
region-of-interest (ROI) within a patient supported on the patient
support 18 in accordance with a treatment plan. In some
embodiments, the therapeutic radiation source 20 may be used for
imaging.
Detector 24 can be coupled to or otherwise supported by the
rotatable gantry 12 and positioned to receive radiation 22 from the
therapeutic radiation source 20. The detector 24 can detect or
otherwise measure the amount of radiation not attenuated and
therefore infer what was in fact attenuated by the patient or
associated patient ROI (by comparison to what was initially
generated). The detector 24 can detect or otherwise collect
attenuation data from different angles as the therapeutic radiation
source 20 rotates around and emits radiation toward the
patient.
It will be further appreciated that the therapeutic radiation
source 20 can include or otherwise be associated with a collimator.
The collimator associated with the therapeutic radiation source 20
can be configured in a number of ways, similar to the
collimator/beamformer 36 associated with the imaging source 30. For
example, a collimator/beamformer can be configured as a multi-leaf
collimator (MLC), which can include a plurality of interlaced
leaves operable to move to one or more positions between a
minimally-open or closed position and a maximally-open position. It
will be appreciated that the leaves can be moved into desired
positions to achieve a desired shape of a radiation beam being
emitted by the radiation source. In one embodiment, the MLC is
capable of sub-millimeter targeting precision.
The therapeutic radiation source 20 may be mounted, configured,
and/or moved into the same plane or a different plane (offset) than
the imaging source 30. In some embodiments, scatter caused by
simultaneous activation of the radiation sources 20, 30 may be
reduced by offsetting the radiation planes.
When integrated with a radiotherapy device, x-ray imaging apparatus
10 can provide images that are used to set up (e.g., align and/or
register), plan, and/or guide a radiation delivery procedure
(treatment). Typical set-up is accomplished by comparing current
(in-treatment) images to pre-treatment image information.
Pre-treatment image information may comprise, for example, computed
tomography (CT) data, cone-beam CT data, magnetic resonance imaging
(MRI) data, positron emission tomography (PET) data or 3D
rotational angiography (3DRA) data, and/or any information obtained
from these or other imaging modalities. In some embodiments, the
x-ray imaging apparatus 10 can track in-treatment patient, target,
or ROI motion.
A reconstruction processor 40 can be operatively coupled to
detector 24 and/or x-ray detector 34. In one embodiment, the
reconstruction processor 40 is configured to generate patient
images based on radiation received by the x-ray detector 34 from
the x-ray source 30. It will be appreciated that the reconstruction
processor 40 can be configured to be used to carry out the methods
described more fully below. The apparatus 10 can also include a
memory 44 suitable for storing information, including, but not
limited to, processing and reconstruction algorithms and software,
imaging parameters, image data from a prior or otherwise
previously-acquired image (e.g., a planning image), treatment
plans, and the like.
The x-ray imaging apparatus 10 can include an operator/user
interface 48, where an operator of the x-ray imaging apparatus 10
can interact with or otherwise control the x-ray imaging apparatus
10 to provide input relating to scan or imaging parameters and the
like. The operator interface 48 can include any suitable input
devices, such as a keyboard, mouse, voice-activated controller, or
the like. The x-ray imaging apparatus 10 can also include a display
52 or other human-readable element to provide output to the
operator of the x-ray imaging apparatus 10. For example, the
display 52 can allow the operator to observe reconstructed patient
images and other information, such as imaging or scan parameters,
related to operation of the x-ray imaging apparatus 10.
As shown in FIG. 2, the x-ray imaging apparatus 10 includes a
controller (indicated generally as 60) operatively coupled to one
or more components of the apparatus 10. The controller 60 controls
the overall functioning and operation of apparatus 10, including
providing power and timing signals to the x-ray source 30 and/or
the therapeutic radiation source 20 and a gantry motor controller
that controls rotational speed and position of the rotatable gantry
12. It will be appreciated that the controller 60 can encompass one
or more of the following: a patient support controller, a gantry
controller, a controller coupled to the therapeutic radiation
source 20 and/or the x-ray source 30, a beamformer 36 controller, a
controller coupled to the detector 24 and/or the x-ray detector 34,
and the like. In one embodiment controller 60 is a system
controller that can control other components, devices, and/or
controllers.
In various embodiments, the reconstruction processor 40, the
operator interface 48, the display 52, the controller 60 and/or
other components may be combined into one or more components or
devices.
The apparatus 10 may include various components, logic, and
software. In one embodiment, the controller 60 comprises a
processor, a memory, and software. By way of example and not
limitation, an x-ray imaging apparatus and/or radiotherapy system
can include various other devices and components (e.g., gantries,
radiation sources, collimators, detectors, controllers, power
sources, patient supports, among others) that can implement one or
more routines or steps related to imaging and/or IGRT for a
specific application, wherein a routine can include imaging,
image-based pre-delivery steps, and/or treatment delivery,
including respective device settings, configurations, and/or
positions (e.g., paths/trajectories), which may be stored in
memory. Furthermore, the controller(s) can directly or indirectly
control one or more devices and/or components in accordance with
one or more routines or processes stored in memory. An example of
direct control is the setting of various radiation source or
collimator parameters (power, speed, position, timing, modulation,
etc.) associated with imaging or treatment. An example of indirect
control is the communication of position, path, speed, etc. to a
patient support controller or other peripheral device. The
hierarchy of the various controllers that may be associated with an
x-ray imaging apparatus can be arranged in any suitable manner to
communicate the appropriate commands and/or information to the
desired devices and components.
Moreover, those skilled in the art will appreciate that the systems
and methods may be implemented with other computer system
configurations. The illustrated aspects of the invention may be
practiced in distributed computing environments where certain tasks
are performed by local or remote processing devices that are linked
through a communications network. For example, in one embodiment,
the reconstruction processor 40 may be associated with a separate
system. In a distributed computing environment, program modules may
be located in both local and remote memory storage devices. For
instance, a remote database, a local database, a cloud-computing
platform, a cloud database, or a combination thereof can be
utilized with x-ray imaging apparatus 10.
X-ray imaging apparatus 10 can utilize an exemplary environment for
implementing various aspects of the invention including a computer,
wherein the computer includes the controller 60 (e.g., including a
processor and a memory, which may be memory 44) and a system bus.
The system bus can couple system components including, but not
limited to the memory to the processor, and can communicate with
other systems, controllers, components, devices, and processors.
Memory can include read only memory (ROM), random access memory
(RAM), hard drives, flash drives, and any other form of computer
readable media. Memory can store various software and data,
including routines and parameters, which may comprise, for example,
a treatment plan.
The therapeutic radiation source 20 and/or x-ray source 30 can be
operatively coupled to a controller 60 configured to control the
relative operation of the therapeutic radiation source 20 and the
x-ray source 30. For example, the x-ray source 30 can be controlled
and operated simultaneously with the therapeutic radiation source
20. In addition, or alternatively, the x-ray source 30 can be
controlled and operated sequentially with the therapeutic radiation
source 20, depending on the particular treatment and/or imaging
plan being implemented.
It will be appreciated that the x-ray source 30 and the x-ray
detector 34 can be configured to provide rotation around the
patient during an imaging scan in a number of ways. In one
embodiment, synchronizing the motion and exposure of the x-ray
source 30 with the longitudinal motion of the patient support 18
can provide a continuous helical acquisition of a patient image
during a procedure. In addition to continuous rotation of the
radiation sources 20, 30 and detector(s) 24, 34 (e.g., continuous
and constant rotation of the gantry with constant patient motion
speed), it will be appreciated that other variations can be
employed without departing from the scope of the disclosed
technology. For example, the rotatable gantry 12 and patient
support can be controlled such that the gantry 12 rotates in a
"back-and-forth" manner (e.g., alternating clockwise rotation and
counterclockwise rotation) around a patient supported on the
patient support (as opposed to continuously, as is described above)
as the support is controlled to move (at a constant or variable
speed) relative to the rotatable gantry 12. In another embodiment,
with successive step-and-shoot circular scans, movement of the
patient support 18 in the longitudinal direction (step) alternates
with a scanning revolution by the rotatable gantry 12 (shoot) until
the desired volume is captured.
Various other types of radiation source and/or patient support
movement may be utilized to achieve relative motion of the
radiation source and the patient for generation of projection data.
Non-continuous motion of the radiation source and/or patient
support, continuous but variable/non-constant (including linear and
non-linear) movement, speed, and/or trajectories, etc., and
combinations thereof may be used, including in combination with the
various embodiments of radiotherapy devices 10 described above.
In one embodiment, the gantry 12 rotation speed, the patient
support 18 speed, the beamformer 36 shape, and/or the detector 34
readout could all be constant during one or more passes of an image
acquisition. In other embodiments, one or more of these variables
could change dynamically during a pass or between passes of an
image acquisition. The gantry 12 rotation speed, patient support 18
speed, beamformer 36 shape, and/or detector 34 readout can be
varied to balance different factors, including, for example, image
quality and image acquisition time.
In other embodiments, these features can be combined with one or
more other image-based activities or procedures, including, for
example, patient set up, adaptive therapy monitoring, treatment
planning, etc.
Images are typically needed at different stages during radiation
treatment. For example, in one treatment fraction, they are used
for patient positioning at an early stage and for dose calculation
at a later stage. Image quality requirements for patient
positioning are less demanding than that on dose calculation. As
mentioned above, images acquired on an IGRT system have two major
uses: treatment setup (e.g., registration with a planning CT image
for patient setup); and treatment planning (e.g., adaptive planning
and/or dose calculation). The requirements of the images for these
two applications can be different. For treatment setup, accuracy in
image quantitation (such as CT numbers) is not as critical as for
treatment planning. For example, a relatively large axial
field-of-view (FOV) imaging may be sufficient for treatment setup,
but not for treatment planning.
For a typical treatment, the total treatment time for each delivery
fraction can include the time for the CT scan, CT reconstruction
time, registration time of the CT image with the planning CT image,
and treatment planning setup time. Conventional IGRT systems
typically acquire one set of CT images for both treatment setup and
treatment planning. In this manner, workflow for patient treatment
may be less than optimal, since image requirements for treatment
setup may be less.
Most IGRT systems with CT scan capabilities use CBCT scans with
circular scans. When a relatively large axial range needs to be
scanned, multiple circular scans can be performed with certain
overlap between neighboring scans. If the image is also used for
dose calculation, then sufficient scanning time is required for
each circular scan to make the image accurate for dose calculation.
The workflow includes waiting until all of the circular scans are
finished and the resulting images are reconstructed before using
the images for registration with the planning CT image and
treatment setup. To improve the overall treatment workflow
(minimizing the total treatment time), one approach includes
reducing the number of circular scans or reducing the scanning time
for each circular scan to achieve a satisfactory compromise among
CT scanning range, scanning time, image quality, and the total
registration/setup time.
An IGRT system with a helical CT scan capability can do a
continuous scan in an axial direction. However, the overall
workflow optimization may also require a compromise between the CT
scanning range, pitch, total scanning time, image quality, and
total registration/setup time.
As described herein, a multi-pass imaging scan can be used to
optimize the workflow, including, for example, reducing the time
required for the pre-delivery steps. The optimization can be
applied via use of an IGRT system with circular and/or helical CT
scan capabilities. Generally, the pre-delivery (and overall
treatment) workflow can be improved by dividing or segmenting an
imaging scan into multiple passes, each acquiring/generating
different and/or complementary data that can be used at different
steps of the workflow. Data can be used (e.g., for reconstruction)
individually or in combination with earlier data. At least one pass
is completed and utilized in less time than it would take to
complete the full imaging scan. A first pass can be optimized to
generate data needed for the initial steps of the workflow, which
can include treatment setup (e.g., registration) and/or any other
treatment pre-planning activities. Once the first pass is complete,
the initial steps of the workflow can begin based on the first pass
data at the same time a second pass of the imaging scan is
executed. The second pass (and any other subsequent passes) can
generate the remaining data needed for the remaining workflow
steps. In some ways, the second pass may be considered as free time
because the patient support has to be moved out of the gantry
anyway--deferring some scanning for during this movement can be a
better utilization of time.
In this manner, the initial steps of the workflow can be started
and completed earlier in the workflow (i.e., rather than waiting
for a complete scan). Furthermore, in various embodiments, total
dosage can be maintained or even reduced via optimization. The
first pass data can be used to determine scanning parameters for
subsequent passes, further optimizing time, image quality, dosage,
etc. In some embodiments, more than two passes can be utilized for
various combinations and workflows with differing improvements.
Different scans of the multi-pass techniques may have different
scan designs (e.g., different parameters). For example, dose,
spectrum (dual energy), view sampling, detector position, detector
resolution, collimation (e.g., 1.sup.st--narrow and
2.sup.nd--wide), energy, scan speed, (including, e.g., pitch),
and/or type (e.g., helical, step-and-shoot, etc.), etc. may be
varied between scans. Various combinations of these parameters
differ in various embodiments.
The systems implementing the imaging scans can include a radiation
source that can be in kV or MV, including with a corresponding kV
or MV detector, as described above. The radiation source can also
include different spectra, which can be, for example, a segmented
or twin-beam like setup using an advanced collimator design. In
some exemplary embodiments, the system may operate at up to 10 rpm
for imaging and 6 rpm for treatment. Conventional CT is too fast
(e.g., around 200 rpm) to implement these techniques. Various beam
shapes, including fan beams and cone beams may be used.
In some embodiments, the first pass is performed with a relatively
short scanning time, but with sufficient image quality for
registration/treatment setup. The second pass can then be performed
after the first pass and while the first pass data is processed
(e.g., reconstructed and registered) for treatment setup to reduce
workflow time. The first pass data can be reconstructed with a fast
reconstruction algorithm and reconstruction parameters (such as
image size) to minimize the reconstruction time. Data from all of
the scan passes can be used to reconstruct a final image using
advanced reconstruction algorithms for treatment planning (e.g.,
dose calculation and adaptive planning).
For example, in one embodiment, the first pass uses a sparse scan
protocol that acquires fewer views of data than a conventional
single scan while the second pass acquires data in another set of
views that are interleaved with the views from the first pass. The
joint data from the two passes will have combined (e.g., full)
views that can be equivalent to or more than a conventional scan.
In another embodiment, the second pass can use a different energy
than the first pass and the joint data of the two passes not only
provides sufficient angular resolution, but also provides spectral
data. In another embodiment, the first pass and the second pass
acquire different numbers of views, such that the joint data have
evenly distributed views angularly or more dense views in some
angular regions than others.
In some embodiments, the first pass image and the planning image,
when registered and analyzed, can provide optimized scanning
parameters for the second pass scan. For example, scan parameters
can be optimized for speed of movement of the patient support,
pitch, collimation, pulse rate of the imaging radiation, energy
level (e.g., "color"), mA (e.g., number of x-rays), and/or gantry
rotational speed. These parameters may also be varied for different
axial regions during the same pass.
In various embodiments, movement of the source of imaging radiation
30 and the radiation detector 34 via the gantry 12 can be
coordinated with movement of the patient support 18 to achieve a
variety of imaging scan designs utilizing multiple scan passes.
These movements can be controlled according to various scan
protocols and the generated projection data processed (e.g.,
including via controller 60 and processor 40) to perform various
steps of the treatment workflow, including, for example, image
reconstruction, registration, related data processing, storage,
communication, etc. within an IGRT system for treatment setup,
treatment planning, and/or treatment delivery. For example, in one
embodiment, step-and-shoot circular scans can be used. In another
embodiment, movement of the patient support 18 and the gantry 12
may be coordinated with constant speeds to perform a helical scan.
In another embodiment, the patient support 18 and/or the gantry 12
moves at a variable speed relative to the other. Speeds of the
patient support 18 and the gantry 12 can be varied such that the
time required to complete the first pass is less than the time
required to complete the second pass, including creating various
pitches of a helical scan or step distances of a circular scan.
For example, in one embodiment, a first pass of an imaging scan is
a fast helical CT scan and the resulting image is reconstructed
with sufficient image quality for treatment setup (e.g.,
registration). While the image is sent to the workstation for
treatment setup, a second pass of the imaging scan is another
helical CT scan performed by reversing the patient table moving
direction. In this embodiment, the registration/treatment setup and
the second pass of the imaging scan can happen simultaneously,
reducing the total workflow time as compared to the conventional
approach of acquiring one set of high-quality CT images for
treatment setup and treatment planning (for each treatment
fraction).
In this embodiment, the second pass can have the same scanning
range as the first pass and the total patient dose can be the same
as or lower than the conventional approach of acquiring one set of
CT images during one pass.
In some embodiments, from the registration and/or setup result
using the first pass data, the second pass scanning parameters may
be adjusted, including, for example, limited to only scan the axial
range of interest, which may be one segment or multiple
segments.
In other embodiments, the first pass may also be used to adjust the
imaging dose at different axial regions during the second pass,
optimizing the dose distribution in the scan range for optimal
image quality in regions where attenuation is more, while the total
patient dose remains the same.
In some embodiments, from the registration results with the
planning CT and/or the treatment pre-planning results using the
first pass data, the second pass may use different scan parameters,
including, for example, a different or varying pitch size in
different axial ranges of the second pass, when higher resolution
in certain axial ranges is desired.
In other embodiments, a multi-pass imaging scan can be used to
generate high quality images quicker, including, for example, by
starting reconstruction of the first pass data during the second
pass, even if treatment setup is not started until completion of
the imaging scan.
For example, this technique may be utilized for generating spectral
images. Two or more helical scan passes of different tube energies
can generate data/images from the multiple CT passes that can be
used to generate spectral images, including electron density
images, material decomposed images, etc. In one embodiment, the
second pass can use a different kV energy than the first pass so
that the two scans can allow spectral CT reconstruction. The
resulting spectral CT can then be used to improve dose calculation
and adaptive planning.
With reference to FIG. 3, an illustration 300 of an x-ray imaging
apparatus 10 is shown with a world coordinate system 310 defined.
The origin, denoted as O, is the iso-center of the gantry 12 and
the unit vectors associated with the x-, y-, and z-axes are shown
as e.sub.x, e.sub.y, and e.sub.z, respectively. Viewing from the
front of the gantry 12, the x-axis e.sub.x is horizontal and points
to the right, the y-axis e.sub.y points into the gantry plane, and
the z-axis e.sub.z is vertical and points to the top. The x-, y-,
and z-axes follow the right-hand rule.
In an exemplary embodiment, the x-ray source 30 rotates clockwise
when viewing from the front of the gantry 12. FIGS. 4-5 illustrate
the movements of the gantry 12 and the patient support 18 during
exemplary passes of an imaging scan. In particular, during the
first pass of a dual-helical scan, the patient support 18 moves
into the gantry 12 (along the y-axis while e.sub.y) the gantry
rotates in an exemplary clockwise direction (around the y-axis
e.sub.y) when looking into the gantry 12. During the second pass of
the dual-helical scan, the patient support 18 moves out of the
gantry 12 while the gantry rotates in the same exemplary clockwise
direction. During the imaging scan, as discussed in more detail
below, the data acquisition in the axial direction may be offset.
In other embodiments, any number of passes may be used to complete
an imaging scan.
In one embodiment, a dual-pass helical scan protocol can be
utilized on an IGRT system with helical scan capability for
improved workflow. In particular, after a patient is positioned on
the patient support 18, a first pass helical scan is performed
while the patient support 18 moves into the gantry 12 (e.g., as
shown in FIG. 4), generating first pass projection data.
Reconstruction of the first pass projection data into a first
patient image can be concurrent with the first pass. A second pass
helical scan is performed after the first pass by reversing the
patient support 18 moving direction so that the patient support 18
moves out of the gantry 12 (e.g., as shown in FIG. 5), for example,
while the other scanning parameters can be kept the same,
generating second pass projection data. The first patient image
from the first pass helical scan can be used for registration with
the planning image and treatment setup while the second pass
helical scan is performed, reducing the total time for the imaging
scan and treatment setup, and in turn, improving the overall
treatment workflow.
In another embodiment, a dual-pass helical scan protocol can be
utilized on an IGRT system with helical scan capability for
differential axial scanning optimization. In particular, a first
pass helical scan is performed while the patient support 18 moves
into the gantry 12 (e.g., as shown in FIG. 4), generating first
pass projection data. Reconstruction of the first pass projection
data into a first patient image can be concurrent with the first
pass. After the first scan, the first patient image is registered
with the planning CT and axial regions are identified for better
resolution or improved statistics. This information can be used to
set or adjust the scan parameters for a second pass helical scan
while the patient support 18 moves out of the gantry 12 (e.g., as
shown in FIG. 5). The identified regions can have the desired
resolution and statistics to improve the accuracy for treatment
planning, including, for example, dose calculation and adaptive
planning.
In another embodiment, a multi-pass helical scan protocol can be
utilized on an IGRT system with helical scan capability for
spectral CT imaging. In particular, a first pass helical CT scan is
performed while the patient support 18 moves into the gantry 12
(e.g., as shown in FIG. 4) using one tube energy and another pass
of the helical CT scan while the patient support 18 moves out of
the gantry 12 (e.g., as shown in FIG. 5) uses a different tube
energy. The multiple passes provide data for spectral CT image
reconstruction. The resulting spectral CT images can be used for
treatment planning, including, for example, accurate dose
calculation and adaptive planning.
In another embodiment, with additional reference to FIG. 6, a
dual-pass helical scan protocol can be utilized with a large pitch
for fast scanning. In this embodiment, a beamformer opening and
detector active area can be one-sided with a very large pitch, such
that during the second pass the beamformer opening and detector
active area is on the other side relative to the first pass with
the same pitch. Exemplary imaging scan design 600 shows the
relative positions of a radiation source 30 and a radiation
detector 34 during two passes of an imaging scan. In particular, a
first pass helical CT scan 610 (Scan I) of an imaging scan is
performed while the patient support 18 moves into the gantry 12
(e.g., as shown in FIG. 4) exposing the detector 34, shown at a
first detector position 612 (Det. Pos. I). A second pass helical CT
scan 620 (Scan II) of the imaging scan is performed while the
patient support 18 moves out of the gantry 12 (e.g., as shown in
FIG. 5) exposing the detector 34, shown at a second detector
position 622 (Det. Pos. II). A large pitch is used for each of the
two passes 610, 620 of the imaging scan, but the detector 34 and
source 30 are shifted in the axial direction (along the y-axis
e.sub.y) during the second pass 620 relative to the first pass 610
so the data from the two passes can be interleaved. When the data
of the dual passes 610, 620 are used jointly, data sufficiency of
the complete imaging scan is improved when compared to each of the
two passes 610, 620, allowing for high quality image
reconstruction. However, the first pass 610 with a large pitch
allows for a faster (and earlier) scan and reconstruction, which
can improve the workflow, for example, when the first pass 610 data
is used for treatment setup during the second pass 620, thereby
reducing the workflow and total treatment time. In different
embodiments, the CT scanning system can be a cone-beam CT system
with a flat-panel CT detector, a conventional multi-detector CT
system, a single row CT system, etc.
In another embodiment, two passes of an imaging scan may include an
offset detector in the scan design. Cone-beam CT (CBCT) is a
prevalent imaging tool for IGRT. A typical CBCT system employs a
flat panel detector 34, which is usually not large enough to
encompass the entire cross section of a patient. An off-centered or
offset detector can be used for circular scans with a large FOV.
Using an off-centered detector configuration during a helical scan
includes substantially more lateral data truncation. Due to such
severe lateral data truncation, image quality is largely dependent
on the helical pitch. Compared to helical scans without lateral
data truncation, the maximum viable pitch of laterally truncated
helical scans drops considerably, and so does the scan speed.
In this embodiment, a two-pass imaging scan for data acquisition
consists of two helices. In the first pass, the patient support 18
moves into the gantry 12 (e.g., as shown in FIG. 4) with the
detector 34 shifted to one lateral side. In the second pass, the
patient support 18 moves out of the gantry 12 (e.g., as shown in
FIG. 5) with the detector 34 shifted to the opposite side. The
lateral detector translation between the two helices are designed
for improved data availability for image reconstruction. Data
acquired from the first pass might be reconstructed for patient
positioning, whereas data from both passes can be used for an
improved image reconstruction that is qualified for dose
calculation. In various embodiments, this type of two-pass helical
imaging scan design may be referred to as a double-helix
trajectory. However, this double-helix trajectory requires a
dedicated image reconstruction algorithm.
The geometry of an exemplary data acquisition system for this
embodiment is shown in FIGS. 7 and 8. As introduced in FIG. 3, the
world coordinate system 310 is spanned by the (x, y, z) axes. FIG.
7 shows an illustration 700 of the 3D geometry of the exemplary
data acquisition system. FIG. 8 shows an illustration 800 of the
geometry of the data acquisition system in an exemplary (x,
z)-plane. In an exemplary embodiment, the x-ray source 30 rotates
clockwise when viewing from the front of the gantry 12. The view
angle, .lamda., is defined as the angular distance from the x-axis
e.sub.x to the virtual line 702 connecting the source 30 and the
rotation axis in a clockwise fashion when looking from the front of
the gantry 12, with its vector position denoted as a(.lamda.). The
rotation axis is along the world coordinate y-axis e.sub.y. The
detector 34 is positioned such that it is perpendicular to the
plane defined by the source 30 and the rotation axis, its channels
are parallel to the rotation axis, and its rows are perpendicular
to the rotation axis. The piercing point of line 702 connecting the
source 30 and the iso-center O at the detector 34 is defined as the
origin of a detector coordinate system 710, which is denoted by
O.sub.d.
As shown in FIG. 7, two coordinate systems are involved with the
exemplary data acquisition system. In particular, the data
acquisition makes reference to the world coordinate system 310 with
origin at O and the detector coordinate system 710 with origin at
O.sub.d. As introduced above, the detector coordinate system 710 is
defined by basis vectors e.sub.u (in the channel direction),
e.sub.v (in the row direction) in the detector 34 plane, and
e.sub.w (perpendicular to the detector 34 plane and pointing from
O.sub.d to a). Here, O.sub.d is defined as the piercing point on
the detector 34 of the line 702 connecting the source 30 (with
vector position a(.lamda.)) and O extended to the detector 34,
along e.sub.w. Whereas .alpha.(.lamda., u, v) is a unit vector 704
pointing from the source 30 vector position a(.lamda.) to the
detector 34 cell located at coordinates [u, v] in the detector
coordinate system 710.
FIG. 8 illustrates the geometry 800 of the data acquisition system
in an exemplary (x, z)-plane. The x-ray source 30 is located in the
(x, z) plane and rotates clockwise around the y axis with a
source-to-isocenter distance (SID) denoted by R. The view or
rotation angle, denoted by .lamda., is defined as the clockwise
angular distance from the x axis. The x-ray source 30 is denoted by
a(.lamda.). The detector 34 is placed 180.degree. apart from the
x-ray source relative to the rotation axis with a
source-to-detector distance (SDD) denoted by D. The detector 34 is
perpendicular to the plane connecting the source 30 and y axis,
with its channels being parallel to the y-axis. The detector plane
is indexed by the (u, v)-coordinate system, with u for the detector
channel position and v for the detector row position.
In this system, the x-ray detector 34 is an exemplary flat panel
detector, and the 2D panel is spanned by the basis vectors e.sub.u
and e.sub.v, with e.sub.u for the channel direction and e.sub.v for
the row direction. The v axis points to the same direction as the y
axis, and the u axis points to the same direction as the rotation
angular velocity. To extend the detector coordinate system to 3D,
reference can be made to the w axis such that (v, u, w) axes follow
the right-hand rule.
As described above, the double-helix scan design includes two
complementary passes with a helical trajectory. FIG. 9A illustrates
the trajectory of an exemplary left-handed helix (LHH) 910 and FIG.
9B illustrates the trajectory of an exemplary right-handed helix
(RHH) 920, both shown with the detector 34 offset. The LHH 910 is
formed by moving the patient support (not shown) into the gantry
with the detector 34 shifted to +u-axis, whereas the RHH 920 is
formed by moving the patient support out of the gantry with the
detector 34 shifted to -u-axis. As shown in this embodiment, the
off-centered detector 34 is large enough that the center x-ray
(through the y axis) is detected and projections to the end of the
shifted direction are not truncated. The pitches of the two helices
910, 920 can be different in general, but are shown here as being
the same.
Regarding image reconstruction, it can be shown that there is only
one .pi.-line available for a point inside the convex hull of a
helix, and that exact image reconstruction of points along a
.pi.-line is possible if the point is visible along the entire
.pi.-line segment. For a typical helical scan with no data
truncation in the lateral direction, this condition is satisfied as
long as the detector is large enough to contain the Tam-Danielsson
(TD) window in the axial direction. This condition is not satisfied
for a large amount of points in the scan field-of-view (SFOV) of a
helical scan with an off-centered detector.
Considering the exemplary double-helix scan design with the
trajectories 910, 920 shown in FIGS. 9A and 9B, an illustration
1000 of data availability in an exemplary transverse plane is shown
in FIG. 10. Depictions of the detector 34 during the exemplary
left-handed helix (LHH) 910 pass and the exemplary right-handed
helix (RHH) 920 pass are shown superimposed in the same transverse
(x, z)-plane 1010. The SFOV is composed of a fully illuminated
region 1020 and a partially illuminated region 1030. By
construction, only the fully illuminated region 1020 is entirely
visible at all azimuth angles, whereas the partially illuminated
region 1030 is only visible by some azimuth angles. For a single
helical scan with an off-centered detector, it can be shown that a
good number of points in the partially illuminated region 1030 may
not be entirely visible along their unique .pi.-line segments, and
thus cannot be exactly and stably recovered. It can also be shown
that for such a trajectory with a large pitch, some points do not
even have 180 degrees of data (relative to the point itself) for
back-projection, which can pose even more difficulty in the
reconstruction task due to the limited angle problem.
The limited angle problem can be avoided in the double-helix
trajectory and thus relaxes the pitch requirement as compared to
the situation of a single helix. One criteria of the pitch
selection for the double-helix trajectory is that, for any point in
the ROI, there is always a large enough azimuth angular range such
that 180 degrees of data are available for back-projection.
Based on the above observation, in this embodiment, the
reconstruction algorithm includes back-projecting all available
data with a weighting mechanism such that all back-projection
weightings at the same azimuth angle and the conjugate azimuth
angle are normalized to 1. Such a weighting mechanism can be
achieved via a pair of weighting functions denoted as w.sup.L and
w.sup.R, for the LHH and RHH respectively. The reconstruction
algorithm is based on a general filtered back-projection (FBP)
framework. Let {circumflex over (f)}.sup.L(x) and {circumflex over
(f)}.sup.R(x) be the reconstructed images using data from the LHH
and RHH, respectively. Let {circumflex over (f)}(x) be the final
reconstruction result.
The LHH reconstruction is described below in equation 1:
.function..intg..LAMBDA..times..times..times..times..times..lamda..times.-
.function..lamda..times..function..lamda..times..function..lamda.
##EQU00001## where (u*, v*) is the piecing point of the x-ray
through x at the detector 34. The term g.sub.H.sup.L in equation 1
is defined as below in equation 2:
g.sub.H.sup.L(.lamda.,u,v)=h.sub.H(u)*g.sub.CB.sup.L'(.lamda.,u,v),
(2) with h.sub.H(u) being the Hilbert transform, and according to
equation 3:
'.function..lamda..times..differential..function..lamda..differential..la-
mda..times..alpha..times..times. ##EQU00002## Here .alpha.(.lamda.,
u, v) is the unit vector pointing from the source a(.lamda.) to the
detector point (u, v), .sup.L(.lamda., u, v) is the projection data
with the laterally truncated data estimated using neighboring
rotations by a known method and g.sub.CB.sup.I/ is view-dependent
differentiation that can be implemented using a known scheme.
The reconstruction from the RHH can be obtained using the same
equations (1, 2, 3) with the superscript L replaced by R. The final
image reconstruction of the double-helix trajectory, {circumflex
over (f)}(x), can be obtained as the sum of {circumflex over
(f)}.sup.L(x) and {circumflex over (f)}.sup.R(x) according to
equation 4: {circumflex over (f)}(x)={circumflex over
(f)}.sup.L(x)+{circumflex over (f)}.sup.R(x) (4)
FIG. 11 shows exemplary reconstructions 1100 of a thorax phantom
using the double-helix scan design and reconstruction technique
described above using a computer simulation. In particular, 1110 is
the reconstruction of the left-handed helix (LHH), 1120 is the
reconstruction of the right-handed helix (RHH), and 1130 is the
reconstruction of the double helix. 1140 is the noiseless data and
1150 is the noisy data. The display window is 1000 HU. In this
example embodiment, computer simulations were performed using a
modified version of the FORBILD thorax phantom. The SID and SDD
were 1080 mm and 1620 mm, respectively. The detector 34 consisted
of 480 channels and 120 rows with pixel size of [0.9 mm, 0.9 mm].
The detector 34 was symmetric about the u axis and was off-centered
along the u axis. The channel offsets were set to 49.75 and 429.75
for the RHH and LHH, respectively. The starting view angles for the
LHH and RHH were 0 and .pi., respectively. Both helices consisted
of 3 rotations with a longitudinal range of 216 mm. For each
detector pixel, the line integral was calculated as the average of
four rays through its corners. Both the LHH and RHH used 480 views
per rotation with pitch of 1. Poisson noise (using 55k photon
counts) and electronic noise (using 5 counts) were added to the
projection data. For image reconstruction, the resolution parameter
.epsilon. was set to 0.05. Image voxels were isotropic with edge
size of 1 mm. These reconstruction results demonstrate that the
reconstruction algorithm is able to recover the FORBILD thorax
phantom with satisfactory image quality.
In this manner, a double-helix trajectory for imaging, including
CBCT during IGRT, can be reconstructed. Compared to a single helix
with laterally off-centered detector, the double-helix trajectory
can improve data availability, improve scan speed, and reduce image
noise. The relation of the configurations between the two helices
can significantly impact the data availability and should be
optimized.
The included flow charts and block diagrams illustrate exemplary
configurations and methodologies associated with multi-pass imaging
scan in accordance with the systems described herein. The exemplary
methodologies may be carried out in logic, software, hardware, or
combinations thereof. In addition, although the procedures and
methods are presented in an order, the blocks may be performed in
different orders, including series and/or parallel. Further,
additional steps or fewer steps may be used.
FIG. 12 is a flow chart of an exemplary multi-pass imaging process
1200. Process 1200 can utilize the imaging systems and scan designs
described above. Exemplary pre-delivery steps of a workflow are
shown as 1202. In this embodiment, an imaging scan is comprised of
at least two passes, with each pass acquiring a portion of the data
needed by the full imaging scan. Each pass can be executed faster
than a full scan. At step 1210, the system executes a first pass of
the imaging scan (e.g., while moving the patient support into the
gantry), generating first pass data 1215. At step 1220, the system
executes a second pass of the imaging scan (e.g., while moving the
patient support out of the gantry), generating second pass data
1225.
In this embodiment, the system can process (e.g., reconstruct) the
first pass data 1215 generated/received during the first pass 1210
while the system executes the second pass 1220. Next, at step 1230,
the system can proceed with various data/image processing and
image-based pre-delivery steps (see, e.g., FIGS. 16-18 below)
including treatment setup (e.g., reconstruction, registration,
alignment, etc.) and treatment planning (e.g., dose calculation,
adaptive planning, etc.). In this manner, the pre-delivery steps
1202 can be completed sooner with a multi-pass imaging scan
(relative to a single pass scan) since image processing of the
first pass data 1215 can occur during the second pass 1220 and
since the time associated with returning the patient support from
inside the gantry can be utilized as scan time in 1220. After
treatment setup/planning 1230 is complete, the process can continue
to treatment delivery at step 1240, including as part of IGRT.
In one embodiment, the first pass 1210 can comprise a first tube
energy of the imaging radiation source and the second pass 1220 can
comprise a second tube energy of the imaging radiation source. The
first pass data 1215 can be reconstructed into a first patient
image and the second pass data 1225 can be reconstructed into a
second patient image such that combining the reconstructed first
and second patient images yields a spectral patient image usable
for various treatment setup and treatment planning tasks, as
described above.
In other embodiments, the imaging scan is comprised of more than
the two passes 1210, 1220. Optional additional pass(es) 1222 and
additional associated pass data 1227 are shown in FIG. 12 to
represent that the imaging scan in these embodiments can include
any number of scan passes.
FIG. 13 is a flow chart of another exemplary multi-pass imaging
process 1300. Process 1300 can utilize the imaging systems and scan
designs described above. Exemplary pre-delivery steps of a workflow
are shown as 1302. In this embodiment, an imaging scan is comprised
of at least two passes, with each pass acquiring a portion of the
data needed by the full imaging scan. Each pass can be executed
faster than a full scan. At step 1310, the system executes a first
pass of the imaging scan (e.g., while moving the patient support
into the gantry), generating first pass data 1315. In this
embodiment, the system can utilize the first pass data 1315
generated/received during the first pass 1310 before or while the
system executes a second pass 1320.
In various embodiments, the raw and/or processed (e.g.,
reconstructed) first pass data 1315 can be used before or while the
system executes the second pass 1320 for determining/adjusting scan
parameters associated with the second pass 1320 (as discussed
above) and for various data/image processing and image-based
pre-delivery steps (see, e.g., FIGS. 16-18 below), including
treatment setup 1330 (e.g., reconstruction, registration,
alignment, etc. as discussed above), and/or treatment pre-planning
1335 (e.g., any treatment planning activities that can be started
and/or based on the first pass data 1315).
At step 1320, the system executes the second pass of the imaging
scan (e.g., while moving the patient support out of the gantry),
generating second pass data 1325. In this embodiment, the system
can start and/or continue to process the first pass data 1315
generated/received during the first pass 1310 while the system
executes the second pass 1320.
Next, at step 1340, the system can utilize the first pass data 1315
and/or the second pass data 1325 (generated/received during the
first pass 1310 and the second pass 1320, respectively) to proceed
with various data/image processing and image-based pre-delivery
steps (see, e.g., FIGS. 16-18 below), including treatment planning
(e.g., dose calculation, adaptive planning, etc.). In some
embodiments, the system can complete tasks at step 1340 that were
started at steps 1330 and/or 1335, including for example, treatment
pre-planning 1335 that needs second pass data 1325 for final
treatment panning 1340.
In this manner, the pre-delivery steps 1302 can be completed sooner
with a multi-pass imaging scan (relative to a single pass scan)
since image processing and utilization of the first pass data 1315
can occur before and/or during the second pass 1320 and since the
time associated with returning the patient support from inside the
gantry can be utilized as scan time in 1320. After treatment
planning 1340 is complete, the process can continue to treatment
delivery at step 1350, including as part of IGRT.
In one embodiment, the first pass data 1315 is of sufficient
quality for treatment setup 1330 such that reconstruction and
registration of the patient image (based on the first pass data
1315) with prior data is underway and/or completed during the
second pass 1320. After the second pass 1320 is complete, the
workflow can proceed directly to treatment planning 1340 based on
the first pass data 1315 and the second pass data 1325.
In other embodiments, the imaging scan is comprised of more than
the two passes 1310, 1320. Optional additional pass(es) 1312, 1322
and additional associated pass data 1317, 1327 are shown in FIG. 13
to represent that the imaging scan in these embodiments can include
any number of scan passes at different points in the workflow
sequence. Furthermore, in various embodiments, raw and/or processed
data from one or more of these passes can be used before or while
the system executes a subsequent pass for determining/adjusting
scan parameters associated with a subsequent pass and/or various
data/image processing and image-based pre-delivery steps, including
treatment setup 1330, and/or treatment pre-planning 1335. For
example, two passes may be executed, generating pass data, which
can be used to determine scan parameters for a subsequent pass,
then the next pass may generate pass data that is then used for
treatment setup in combination with previous pass data. As can be
appreciated, any number of scan passes can generate pass data that
can be utilized in various combinations for any of the workflow
steps.
FIG. 14 is a flow chart of another exemplary multi-pass imaging
process 1400. Process 1400 can utilize the imaging systems and scan
designs described above. In this embodiment, an imaging scan is
comprised of at least two passes, with each pass acquiring a
portion of the data needed by the full imaging scan. Each pass can
be executed faster than a full scan. At step 1410, the system
executes a first pass of the imaging scan (e.g., while moving the
patient support into the gantry), generating first pass data 1415.
In this embodiment, the system can utilize the first pass data 1415
generated/received during the first pass 1410 before or while the
system executes a second pass 1420.
In this embodiment, the raw and/or processed (e.g., reconstructed)
first pass data 1415 is used for treatment setup 1430 (e.g.,
registering a first patient image (based on the first pass data
1415) with prior data 1405) before or while the system executes the
second pass 1420. Optionally (depicted in FIG. 14 by dashed line),
in some embodiments, the raw and/or processed first pass data 1415
can also be used before the system executes the second pass 1420
for determining/adjusting scan parameters associated with the
second pass 1320 (as discussed above).
At step 1420, the system executes the second pass of the imaging
scan (e.g., while moving the patient support out of the gantry),
generating second pass data 1425. In this embodiment, the system
can start and/or continue treatment setup 1430 using the first pass
data 1415 generated/received during the first pass 1410 while the
system executes the second pass 1420.
Next, at step 1440, the system utilizes the first pass data 1415
and the second pass data 1425 for treatment planning (e.g., dose
calculation, adaptive planning, etc.). In some embodiments, the
prior data 1405 is also utilized for treatment planning 1440
tasks.
In this manner, pre-delivery workflow steps treatment setup 1430
and treatment planning 1440 are completed sooner with the
multi-pass imaging scan (1410+1420) than a single pass scan, since
treatment setup 1430 utilizes the first pass data 1415 before
and/or during the second pass 1420 and since the time associated
with returning the patient support from inside the gantry can be
utilized as scan time in 1420. After treatment planning 1440 is
complete, the process can continue to treatment delivery, including
as part of IGRT.
FIG. 15 is a flow chart of another exemplary multi-pass imaging
process 1500. Process 1500 can utilize the imaging systems and scan
designs described above. In this embodiment, an imaging scan is
comprised of at least two passes, with each pass acquiring a
portion of the data needed by the full imaging scan. Each pass can
be executed faster than a full scan. At step 1510, the system
executes a first pass of the imaging scan (e.g., while moving the
patient support into the gantry), generating first pass data 1515.
In this embodiment, the system can utilize the first pass data 1515
generated/received during the first pass 1510 before or while the
system executes a second pass 1520.
In this embodiment, first pass data 1515 is reconstructed at step
1520 using a reconstruction technique suitable for the projection
data 1515, generating a patient image 1525. Next, at step 1530, the
patient image 1525 is registered with prior image data 1505 for
treatment setup before or while the system executes the second pass
1540. Optionally (depicted in FIG. 15 by dashed lines), in some
embodiments, projection data 1515, patient image 1525, and/or a
registered image from 1530 can also be used before the system
executes the second pass 1540 for determining/adjusting scan
parameters associated with the second pass 1540 (as discussed
above).
At step 1540, the system executes the second pass of the imaging
scan (e.g., while moving the patient support out of the gantry),
generating second pass data 1545. In this embodiment, the system
can start and/or continue reconstruction 1520 and/or registration
1530 using the first pass data 1515 generated/received during the
first pass 1510 while the system executes the second pass 1540.
Next, at step 1550, the system utilizes the first pass data 1515
and the second pass data 1545 to reconstruct patient image 1555. At
step 1560, the patient image 1555 is utilized to calculate a
treatment dose. In some embodiments, the prior data 1505 is also
utilized for dose calculation 1560.
In this manner, pre-delivery workflow steps 1520, 1530, 1550, 1560
are completed sooner with the multi-pass imaging scan (1510+1540)
than a single pass scan, since reconstruction 1520 and registration
1530 steps utilize the first pass data 1515 before and/or during
the second pass 1540 and since the time associated with returning
the patient support from inside the gantry can be utilized as scan
time in 1540. After dose calculation 1560 is complete, the process
can continue to treatment delivery, including as part of IGRT.
In all of these embodiments, various scan designs may be used,
including various designs for the passes comprising the imaging
scan. For example, as described above, the patient support 18 can
move in a first longitudinal direction during the first pass (e.g.,
into the gantry 12) and move in a second longitudinal direction
during the second pass (e.g., out of the gantry 12), where the
second direction is opposite the first direction. However, in other
embodiments, different passes may be in the same direction. The
passes may comprise different patient support 18 and/or gantry 12
speeds, which both may be constant or variable. The passes can also
be completed in the same or different times (e.g., where a first
pass is completed in less time than a second pass). The passes can
also include more or less views than other passes. The pass
trajectories can be helical and/or circular (e.g., step-and-shoot,
where a series of steps/shoots comprise one pass). Passes can
include periods of time when the imaging radiation source is not
active, including effectively skipping portions of the patient.
In some embodiments, an axial position of the imaging radiation
source 30 and the detector 34 is shifted between passes, including
where the data from different passes are complementary during
reconstruction of a patient image. In one embodiment, the detector
34 is offset in one transaxial direction during a first pass and
offset in an opposite transaxial direction during a second pass,
including to accommodate a large FOV.
These techniques can be used for IGRT workflow improvements and
optimization and CT image quality and quantitation improvements for
dose calculation and adaptive planning.
FIG. 16 is a flow chart depicting an exemplary method 1600 of IGRT
using a radiotherapy device (including, e.g., x-ray imaging
apparatus 10). Prior data 1605 can include images of the patient
(e.g., a prior image, which may be a previously-acquired planning
image, including a prior CT image, as discussed above), treatment
plans, phantom information, models, a priori information, etc. In
some embodiments, the prior data 1605 is generated by the same
radiotherapy device, but at an earlier time. At step 1610, imaging
(including multi-pass imaging) of a patient is performed using a
source of low-energy radiation (e.g., kV radiation from x-ray
source 30). In various embodiments, imaging comprises a helical or
circular scan with a fan or cone beam geometry. Step 1610 can
produce high-quality (HQ) image(s) or imaging data 1615 using the
techniques described above. In some embodiments, image quality may
be adjusted to optimize a balance between image quality/resolution
and dosage. In other words, not all images need to be of the
highest quality or image quality may be adjusted to optimize or
trade off a balance between image quality/resolution and image
acquisition time. Imaging step 1610 also includes image processing
1620 to generate patient images based on the imaging/scan data 1615
(e.g., in accordance with embodiments described above). Although
image processing step 1620 is shown as part of imaging step 1610,
in some embodiments image processing step 1620 is a separate step,
including where image processing is executed by separate
devices.
Next, at step 1630, one or more image-based pre-delivery steps,
discussed below, are performed based at least in part on the
imaging data 1615 from step 1610. As discussed in more detail
below, step 1630 can include determining various parameters
associated with the therapeutic treatment and (subsequent) imaging
planning. In some embodiments, image-based pre-delivery steps
(1630) may require more imaging (1610) before treatment delivery
(1640). Step 1630 can include adapting a treatment plan based on
the high-quality imaging data 1615 as part of an adaptive
radiotherapy routine. In some embodiments, image-based pre-delivery
steps 1630 may include real-time treatment planning. Embodiments
may also include simultaneous, overlapping, and/or alternating
activation of the imaging and therapeutic radiation sources.
Real-time treatment planning may involve any or all of these types
of imaging and therapeutic radiation activation techniques
(simultaneous, overlapping, and/or alternating).
Next, at step 1640, therapeutic treatment delivery is performed
using a source of high-energy radiation (e.g., MV radiation from
therapeutic radiation source 20). Step 1640 delivers a treatment
dose 1645 to the patient according to the treatment plan. In some
embodiments, the IGRT method 1600 may include returning to step
1610 for additional imaging at various intervals, followed by
image-based pre-delivery steps (1630) and/or treatment delivery
(1640) as required. In this manner the high-quality imaging data
1615 may be produced and utilized during IGRT using one apparatus
10 that is capable of adaptive therapy. As mentioned above, steps
1610, 1630, and/or 1640 may be executed simultaneously,
overlapping, and/or alternating.
IGRT can include at least two general goals: (i) to deliver a
highly conformal dose distribution to the target volume; and (ii)
to deliver treatment beams with high accuracy throughout every
treatment fraction. A third goal can be to accomplish the two
general goals in as little time per fraction as possible.
Delivering treatment beams accurately requires the ability to
identify and/or track the location of the target volume
intrafraction with high-quality images. The ability to increase
delivery speed requires the ability to accurately, precisely, and
quickly perform imaging 1610, image-based pre-delivery steps 1630,
and treatment delivery 1640, including moving the radiation source
according to the treatment plan.
The imaging and processing techniques described above to support
quicker pre-delivery workflows, including multi-pass imaging scans,
treatment set-up, treatment pre-planning, and treatment planning
steps are included in the imaging 1610 and image-based pre-delivery
steps 1630 described herein, including as part of an IGRT
workflow.
FIG. 17 is a block diagram 1700 depicting exemplary image-based
pre-delivery steps/options that may be associated with step 1630
above. It will be appreciated that the above-described x-ray
imaging apparatus 10 (e.g., as part of a radiotherapy device) can
generate kV images that can be used in a variety of ways, including
for image-based pre-delivery steps (1630), without departing from
the scope of the present invention. For example, images 1615
generated by the radiotherapy device can be used to align a patient
prior to treatment (1710). Patient alignment can include
correlating or registering the current imaging data 1615 with
imaging data associated with earlier pre-treatment scans and/or
plans, including the treatment plan. Patient alignment can also
include feedback on the physical position of the patient relative
to the radiation source to verify whether the patient is physically
within the range of the delivery system. If necessary, the patient
can be adjusted accordingly. In some embodiments, patient alignment
imaging may purposely be of lesser quality to minimize dosage but
provide adequate alignment information.
Images generated by the x-ray imaging apparatus 10 can also be used
for treatment planning or re-planning (1720). In various
embodiments, step 1720 can include confirming the treatment plan,
modifying the treatment plan, generating a new treatment plan,
and/or choosing a treatment plan from a set of treatment plans
(sometimes referred to as "plan of the day"). For example, if the
imaging data 1615 shows that the target volume or ROI is the same
as when the treatment plan was developed, then the treatment plan
can be confirmed. However, if the target volume or ROI is not the
same, re-planning of the therapeutic treatment may be necessary. In
the case of re-planning, because of the high quality of the imaging
data 1615 (generated by the x-ray imaging apparatus 10 at step
1610), the imaging data 1615 may be used for treatment planning or
re-planning (e.g., generating a new or modified treatment plan). In
this manner, pre-treatment CT imaging via a different device is not
necessary. In some embodiments, confirming and/or re-planning may
be an ongoing procedure before and/or after various treatments.
In accordance with another exemplary use case, images generated by
the x-ray imaging apparatus 10 can be used to calculate imaging
dose (1730), which may be used for ongoing determinations of total
dose to the patient and/or for subsequent imaging planning. The
quality of subsequent imaging may also be determined as part of the
treatment planning, for example, to balance quality and dosage. In
accordance with another exemplary use case, images generated by the
x-ray imaging apparatus 10 can be used to calculate treatment dose
(1740), which may be used for ongoing determinations of total dose
to the patient and/or may be included as part of treatment planning
or re-planning.
In accordance with other exemplary use cases, images generated by
the x-ray imaging apparatus 10 can be used in connection with
planning or adjusting other imaging (1750) and/or other treatment
(1760) parameters or plans, including, for example, as part of
adaptive therapy and/or treatment plan generation. In accordance
with another exemplary use case, images generated by the x-ray
imaging apparatus 10 can be used in connection with adaptive
therapy monitoring (1770), which can include monitoring treatment
delivery and adapting as required.
It should be appreciated that the image-based pre-delivery steps
(1630) are not mutually exclusive. For example, in various
embodiments, calculate treatment dose (1740) can be a step by
itself and/or can be part of adaptive therapy monitoring (1770)
and/or treatment planning (1720). In various embodiments, the
image-based pre-delivery steps (1620) can be performed
automatically and/or manually with human involvement.
The devices and methods described above, including the offset
detector and data processing techniques, can provide improved
kV-generated images of higher quality than conventional
in-treatment imaging systems.
FIG. 18 is a block diagram 1800 depicting exemplary data sources
that may be utilized during imaging (1610) and/or subsequent
image-based pre-delivery steps (1630). Detector data 1810
represents all of the data received by the image radiation detector
34. The projection data 1820 is the data generated by the radiation
incident in the collimated beam area. The penumbra data 1830 is the
data generated by the radiation incident in the penumbra area. The
scatter data 1840 is the data generated by the radiation incident
in the peripheral area outside of the penumbra area, which may be
referred to as the shadow region(s).
In one embodiment, the penumbra data 1830 may be used to separate
or identify the projection and/or scatter data. In some
embodiments, the scatter data 1840 can be used to estimate the
scatter radiation in the projection data 1820. In another
embodiment, the scatter data 1840 can be used to determine the
residual effect of the scatter from the therapeutic radiation
source 20 (e.g., MV) when the two sources 20, 30 are operated
simultaneously or in an interleaved manner.
In this manner, the penumbra data 1830 and/or the scatter data 1840
may be utilized to improve the quality of the images generated by
the imaging step 1610. In some embodiments, the penumbra data 1830
and/or the scatter data 1840 may be combined with the projection
data 1820 and/or analyzed in view of the applicable imaging
settings 1850, treatment settings 1860 (e.g., if simultaneous
imaging and treatment radiation), and any other data 1870
associated with the x-ray imaging apparatus 10 at the time of the
data collection at the imaging detector 34. In other embodiments,
the data may be used for the treatment planning step 1630.
Although the disclosed technology has been shown and described with
respect to a certain aspect, embodiment or embodiments, it is
obvious that equivalent alterations and modifications will occur to
others skilled in the art upon the reading and understanding of
this specification and the annexed drawings. In particular regard
to the various functions performed by the above described elements
(components, assemblies, devices, members, compositions, etc.), the
terms (including a reference to a "means") used to describe such
elements are intended to correspond, unless otherwise indicated, to
any element which performs the specified function of the described
element (i.e., that is functionally equivalent), even though not
structurally equivalent to the disclosed structure which performs
the function in the herein illustrated exemplary aspect, embodiment
or embodiments of the disclosed technology. In addition, while a
particular feature of the disclosed technology may have been
described above with respect to only one or more of several
illustrated aspects or embodiments, such feature may be combined
with one or more other features of the other embodiments, as may be
desired and advantageous for any given or particular
application.
While the embodiments discussed herein have been related to the
systems and methods discussed above, these embodiments are intended
to be exemplary and are not intended to limit the applicability of
these embodiments to only those discussions set forth herein. While
the present invention has been illustrated by the description of
embodiments thereof, and while the embodiments have been described
in some detail, it is not the intention of the applicant to
restrict or in any way limit the scope of the appended claims to
such detail. Additional advantages and modifications will readily
appear to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details,
representative apparatus and methods, and illustrative examples
shown and described. Accordingly, departures may be made from such
details without departing from the spirit or scope of the
applicant's general inventive concept.
* * * * *